Patent application title: Vibration damping apparatus

Abstract:

A vibration damping apparatus wherein a mass member is elastically
supported by a spring member on a vibrating member to be damped for
constituting a secondary vibrating system. The spring member is a metal
plate spring with one end being attached to the mass member and the other
end being attached to the vibrating member. A rubber bushing having an
inner and an outer tube member positioned spaced apart from one another
in a diametrical direction and linked in the diametrical direction by a
rubber elastic body. One of the inner shaft member and the outer tube
member of the rubber bushing is fastened to the plate spring while the
other is fastened to the mass member or the vibration damping apparatus,
whereby the moment is exerted in the torsional direction of the rubber
bushing during displacement of the mass member by vibration to be damped.

Claims:

1. A vibration damping apparatus comprising:a mass member; anda spring
member for elastically supporting the mass member on a vibrating member
to be damped for constituting a secondary vibrating system for the
vibrating member, the spring member comprising at least one plate spring
of metal, one end of the plate spring being attached to the mass member
and the other end of the plate spring being attached to the vibrating
member; anda rubber bushing having an inner shaft member and an outer
tube member positioned spaced apart from one another in a diametrical
direction and linked in the diametrical direction by a rubber elastic
body, the rubber bushing being positioned at a mounting location of the
plate spring to at least one of the mass member and the vibrating member,
with one of the inner shaft member and the outer tube member of the
rubber bushing fastened to the plate spring while the other of the inner
shaft member and the outer tube member is fastened to the mass member or
the vibration damping apparatus where the rubber bushing is positioned,
whereby moment is exerted in a torsional direction of the rubber bushing
during displacement of the mass member by vibration to be damped.

2. The vibration damping apparatus according to claim 1, wherein the
spring member comprises a plurality of plate springs of metal, and at
least one plate spring is positioned at a location away from at least
another plate spring in a direction of vibration to be damped.

3. The vibration damping apparatus according to claim 1, wherein the
spring member comprises a plurality of plate springs of metal, and a
center axis of elastic support composed of the plurality of plate springs
coinciding with a vertical direction passing through a center of gravity
of the mass member.

4. The vibration damping apparatus according to claim 1, wherein a pair of
the plate springs are constituted using a single plate spring stuff, by
fastening a lengthwise center section of the plate spring stuff to the
mass member with two end sections of the plate spring stuff projecting to
either side in a horizontal direction from the mass member; and attaching
the rubber bushing to a distal end portion of each of the pair of the
plate springs that project out from the mass member.

5. The vibration damping apparatus according to claim 4, wherein a center
axis of elastic support composed of the pair of the plate springs
coincides with a vertical direction passing through a center of gravity
of the mass member, and the distal end portion of each of the pair of the
plate springs is attached to the vibrating member via the rubber elastic
body of the rubber bushings, and attached such that a direction of input
load exerted on the plate spring stuffs by the mass member during
vibration input will exert moment in a circumferential direction of the
rubber elastic body which has round tubular shape.

6. The vibration damping apparatus according to claim 1, wherein the plate
spring has a bending portion that appears bent in side view, situated
between a location of attachment to the mass member and a location of
attachment to the vibrating member.

7. The vibration damping apparatus according to claim 1, wherein the mass
member is constituted by a damper mass having an independent mass member
positioned housed within a housing space formed in an interior of a
hollow housing, with a minute gap provided between the independent mass
member and an inside wall of the housing space to permit free
displacement of the independent mass member independently of the hollow
housing.

Description:

INCORPORATED BY REFERENCE

[0001]The disclosure of Japanese Patent Application No. 2007-035794 filed
on Feb. 16, 2007, including the specification, drawings and abstract is
incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a vibration damping apparatus that
constitutes a secondary vibrating system for a vibrating member to be
vibration-damped, and that is adapted to reduce vibration of a vibrating
member in a primary vibrating system. More particularly, the present
invention relates to a vibration damping apparatus of novel construction
affording outstanding vibration damping action against low-frequency,
large amplitude vibration by a vibrating member of large mass.

[0004]2. Description of the Related Art

[0005]A dynamic damper composed of a mass-spring system and designed to be
attached to a vibrating member of a primary vibrating system, in order to
constitute a secondary vibrating system therefor, is known in the art as
one type of vibration damping apparatus adapted to reduce vibration in
vibrating members whose vibration poses a problem, such as the body of a
car. Such an apparatus is disclosed in U.S. Pat. No. 6,991,077, for
example.

[0006]The frame of a car body may be subjected to input of low-frequency,
large amplitude vibration when, for example, the car drives over a bump.
Due to the large mass of the car body frame, it will be necessary to use
a component of large mass as a mass member, in order to effectively damp
such vibration. Given that the mass member has a large mass, it will be
necessary to establish a sufficiently low spring constant in order to set
the tuning frequency of the secondary vibrating system constituted by the
mass-spring system within a low-frequency range.

[0007]In typical dynamic dampers employing a compression rubber elastic
body as the spring member, is was necessary for the member to have a
small cross-sectional area in order to achieve the desired low spring
constant. However this arrangement created the problem that it becomes
difficult to ensure sufficient support strength for such a mass member of
large mass.

[0008]It has also been contemplated to use a plate spring made of metal,
in order to achieve low spring constant while ensuring adequate support
strength.

[0009]However, due to the use of mass members having large mass, the use
of metal plate springs poses a concern with regard stress concentrations
arising in fastening locations to the mass member and to the supporting
member (damped member), and to possible fatigue rupture caused thereby.
Particularly where a "cantilever structure" by the plate spring for the
mass member has been employed, durability of the plate spring will tend
to become a greater problem.

[0010]In order to alleviate the problem of stress concentration in the
plate spring, a "both-sides holding structure" whereby the mass member is
supported from both the left and right sides by respective plate springs
could also be contemplated. However, where such a both-sides holding
structure is employed for the mass member, since the plate springs per se
undergo substantially no elongation or contraction in the lengthwise
direction, during displacement of the mass member they will not be able
to respond to changes in distance between the mass member and the
supporting member which are linked by the plate springs. As a result, the
linear region of the mass-spring system will be extremely small due to
the tensile rigidity of the plate springs in their lengthwise direction,
creating the problem of difficultly in achieving the required vibration
damping action against low-frequency, large amplitude vibration in
particular.

[0011]In order to address the problem of stress concentration in the plate
spring and of ensuring an adequate linear region, it could be
contemplated to employ a sufficient length for the plate springs, for
example. However, achieving satisfactory characteristics would require
excessive plate spring length dimension, making the dynamic damper much
too large for practical purposes, and accordingly this is not an
effective solution.

SUMMARY OF THE INVENTION

[0012]It is an object of the present invention to provide a vibration
damping apparatus of novel structure that, while maintaining compact size
and excellent durability, affords substantially linear spring
characteristics over a large region of displacement by the mass member,
and that thereby exhibits excellent vibration damping action against
low-frequency, large amplitude vibration input by a vibrating member
having large mass.

[0013]The above and/or optional objects of this invention may be attained
according to at least one of the following modes of the invention. The
following modes and/or elements employed in each mode of the invention
may be adopted at any possible optional combinations.

[0014]A first mode of the invention provides a vibration damping apparatus
a vibration damping apparatus comprising: a mass member; and a spring
member for elastically supporting the mass member on a vibrating member
to be damped for constituting a secondary vibrating system for the
vibrating member, the spring member comprising at least one plate spring
of metal, one end of the plate spring being attached to the mass member
and the other end of the plate spring being attached to the vibrating
member; and a rubber bushing having an inner shaft member and an outer
tube member positioned spaced apart from one another in a diametrical
direction and linked in the diametrical direction by a rubber elastic
body, the rubber bushing being positioned at a mounting location of the
plate spring to at least one of the mass member and the vibrating member,
with one of the inner shaft member and the outer tube member of the
rubber bushing fastened to the plate spring while the other of the inner
shaft member and the outer tube member is fastened to the mass member or
the vibration damping apparatus where the rubber bushing is positioned,
whereby moment is exerted in a torsional direction of the rubber bushing
during displacement of the mass member by vibration to be damped.

[0015]In the vibration damping apparatus of structure according to this
mode, by employing a plate spring of metal, the spring constant of the
secondary vibrating system can be set to a very low level, whereby
effective vibration damping action against low-frequency vibration can be
achieved. In the present mode, in the event of appreciable displacement
the mass member caused by input of high-amplitude vibration etc., moment
will be exerted in the torsional direction on the rubber elastic body
provided to the rubber bushing, inducing deformation of the rubber
elastic body. This will permit change in the distance between the plate
spring support points, i.e. in the distance between the plate spring
location of attachment to the mass member and the location of attachment
to the vibrating member, as the rubber elastic body is induced to deform;
and inhibit sharp change in characteristics of the plate spring due to
tensile rigidity of the plate spring. As a result, substantially linear
characteristics will be achieved across the region of displacement of the
mass member, and it will be possible to consistently use the bending
elasticity of the plate spring and achieve excellent vibration damping
action against low-frequency vibration as well.

[0016]Moreover, since a large region giving linear characteristics of the
plate spring is assured, it is possible to expand the possible tuning
range for vibration damping without having to increase the length
dimension of the plate spring, and the vibration damping apparatus can be
compact in size while durability of the plate spring is improved.
Furthermore, due to attenuating action by the rubber elastic body, it is
possible to suppress the peaks in the vibration transmission rate
observed respectively in frequency regions both on the low-frequency end
and the high-frequency end of the tuning frequency band of the secondary
vibrating system in the vibrating member of the primary vibrating system,
making it possible to achieve good vibration damping action across the
entirety of a wide frequency range.

[0017]Additionally, in the present mode, by employing the rubber bushing
it is possible to achieve consistent elasticity both with respect to
moment of the plate spring acting on the linking section with the plate
spring, and to tensile load of the plate spring. Specifically, for the
purpose of permitting change of distance between the plate spring support
points during displacement of the mass member, it would be conceivable,
for example, to use a rubber plate and permit change of distance between
the plate spring support points through shear deformation of the rubber
plate. However, with a rubber plate it is difficult to ensure adequate
durability with respect to a mass member of large mass, and it will be
necessary to devise some failsafe mechanism against fatigue rupture etc.
caused thereby. A further problem with a rubber plate is that it is
difficult to deal with change in the load input direction exerted during
displacement of the mass member.

[0018]On the other hand, where a rubber bushing of structure according to
the present invention is employed, the moment of the plate spring will be
exerted in the torsional direction of the rubber elastic body, thus
achieving low spring characteristics in the rotational direction with
respect to the rubber bushing, and achieving high spring characteristics
in the axis-perpendicular direction to the rubber elastic body while
permitting the distance between the plate spring support points to change
easily during displacement of the mass member, whereby durability with
respect to a mass member of large mass may be assured as well. Moreover,
because the inner shaft member passes through the outer tube member, if
for example the rubber elastic body should rupture, the mass member will
be prevented from separating from the supporting member (damped member),
thus achieving a failsafe mechanism without the need to provide any
special structure.

[0019]A second mode of the present invention provides the vibration
damping apparatus according to the first mode, wherein the spring member
comprises a plurality of plate springs of metal, and at least one plate
spring is positioned at a location away from at least another plate
spring in a direction of vibration to be damped.

[0020]In the vibration damping apparatus of structure according to this
mode, the mass member is supported from both sides in the vibrating
direction. The mass member can be supported more stably thereby, and
tilting or other such irregular displacement of the mass member can be
inhibited when vibration is input, thereby affording more consistent
vibration damping action.

[0021]A third mode of the present invention provides the vibration damping
apparatus according to the first or second mode, wherein the spring
member comprises a plurality of plate springs of metal, and a center axis
of elastic support composed of the plurality of plate springs coinciding
with a vertical direction passing through a center of gravity of the mass
member.

[0022]In the vibration damping apparatus of structure according to this
mode, it is possible to inhibit irregular displacement in the twisting
direction etc. during displacement of the mass member, and to achieve
more consistent deformation of the plate springs and displacement of the
mass member in the vertical direction. Consequently, more consistent and
efficient vibration damping action can be achieved.

[0023]A fourth mode of the present invention provides the vibration
damping apparatus according to any one of the first through third modes,
wherein a pair of the plate springs are constituted using a single plate
spring stuff, by fastening a lengthwise center section of the plate
spring stuff to the mass member with two end sections of the plate spring
stuff projecting to either side in a horizontal direction from the mass
member; and attaching the rubber bushing to a distal end portion of each
of the pair of the plate springs that project out from the mass member.

[0024]In the vibration damping apparatus of structure according to this
mode, the mass member has a "both sides supporting structure" supported
by the center section of a single plate spring stuff. The mass member can
therefore be supported more stably than with a "single cantilever
structure" in which it is supported on one side, and support of the mass
member is distributed between the two sides of the plate spring stuff,
whereby the durability of the plate spring can be improved.

[0025]Moreover, since the mass member is fastened to the center section of
the plate spring stuff, it is a simple matter to arrange the center axis
of elastic support of the plate spring so as to pass through the center
of gravity of the mass member, whereby the structure according to the
preceding third mode can be realized easily.

[0026]It should be appreciated that the plate spring in the present
invention refers to a member extending between the mass member and the
vibrating member. It is not necessary for a single plate spring to be
composed of a single independent component. For example, in the present
mode, each plate spring is constituted by a section of a plate spring
stuff which extends from the center section to one end section thereof,
whereby a pair of plate springs are constituted by the single plate
spring stuff.

[0027]A fifth mode of the present invention provides the vibration damping
apparatus according to any one of the first through fourth modes, wherein
the plate spring has a bending portion that appears bent in side view,
situated between a location of attachment to the mass member and a
location of attachment to the vibrating member.

[0028]In the vibration damping apparatus of structure according to this
mode, by imparting the plate spring with a bending portion, the bending
portion of the plate spring will undergo extension and contraction in the
event of appreciable displacement of the mass member caused by input of
large-amplitude vibration. Thus, a larger substantial length dimension
for the plate spring can be assured, thereby permitting change in
distance between the plate spring support points in association with
displacement of the mass member. Consequently, deformation of the rubber
elastic body of the rubber bushing, and linear characteristics of the
plate spring in cooperation with expanding/contracting deformation of the
bending portion, can be assured over a wider range, and thus better
vibration damping action can be achieved.

[0029]A sixth mode of the present invention provides the vibration damping
apparatus according to any one of the first through fifth modes, wherein
the mass member is constituted by a damper mass having an independent
mass member positioned housed within a housing space formed in an
interior of a hollow housing, with a minute gap provided between the
independent mass member and an inside wall of the housing space to permit
free displacement of the independent mass member independently of the
hollow housing.

[0030]In the vibration damping apparatus of structure according to this
mode, input of vibration inducing displacement of the damper mass will
cause the independent mass member to undergo ricochet displacement with
respect to the hollow housing and strike into contact against it.
Amplitude-reducing effect on the vibrating member will be produced on the
basis of this contact against the hollow housing by the independent mass
member. Moreover, a state substantially identical to a greater apparent
loss coefficient will be observed in the secondary vibrating system
composed of the damper mass and the plate spring, and the peaks of
vibration transmission rate observed respectively in frequency regions
both on the low-frequency end and the high-frequency end of the tuning
frequency of the secondary vibrating system in the vibrating member of
the primary vibrating system will be suppressed, making it possible to
achieve good vibration damping action across the entirety of a wide
frequency range.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]The foregoing and/or other objects features and advantages of the
invention will become more apparent from the following description of a
preferred embodiment with reference to the accompanying drawings in which
like reference numerals designate like elements and wherein:

[0032]FIG. 1 is a vertical cross sectional view of a vibration damping
apparatus of construction according to a first embodiment of the present
invention;

[0033]FIG. 2 is an enlarged vertical cross sectional view of an
independent mass member of the vibration damping apparatus of FIG. 1;

[0034]FIG. 3 is a top plane view of a plate spring of the vibration
damping apparatus of FIG. 1;

[0035]FIG. 4 is a top plane view of an attachment portion of the plate
spring of the vibration damping apparatus of FIG. 1;

[0036]FIG. 5 is a graph demonstrating spring characteristics of the
vibration damping apparatus of FIG. 1 together with a result of
measurements regarding a comparative example; and

[0037]FIG. 6 is a vertical cross sectional view of a vibration damping
apparatus of construction according to a second embodiment of the present
invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038]FIG. 1 depicts a vibration damping apparatus 10 pertaining to a
first embodiment of the present invention. The vibration damping
apparatus 10 includes a damper mass 14 constituting a mass member
elastically supported with respect to a pair of brackets 12a, 12b by a
pair of plate spring stuffs 16 constituting the plate spring stuffs, and
rubber bushings 18 attached to these plate spring stuffs 16 at both ends.
The brackets 12a, 12b are attached to a vibrating member 20 such as the
body frame of a car, while the damper mass 14 is elastically supported by
the plate spring stuffs 16 and the rubber bushings 18 with respect to the
vibrating member 20, thereby constituting a secondary vibrating system
for the vibrating member 20 of the primary vibrating system. FIG. 1
depicts the plate spring stuffs 16 displaced slightly downward (downward
in FIG. 1) due to the effect of gravity on the damper mass 14 in the
stationary state. Unless indicated otherwise, vertical direction herein
refers to the vertical direction in FIG. 1, and in the present
embodiment, the vertical direction is the plumb-vertical direction as
well.

[0039]To describe in greater detail, the damper mass 14 is composed of an
upper damper mass 22a and a lower damper mass 22b of mutually similar
structure, attached together with a fastener plate 24 having a generally
rectangular shape of prescribed thickness. Since the upper damper mass
22a and the lower damper mass 22b have mutually similar structure, the
following discussion will take the upper damper mass 22a by way of
example.

[0040]The upper damper mass 22a includes a hollow housing 28 having a
number (in the present embodiment, three) of housing spaces 26 formed in
its interior; and mass members 30 constituting independent mass members,
housed within each of the housing spaces 26. The hollow housing 28 has an
overall shape resembling a battery of three inverted cups, produced by
arranging three bottomed tubes open at the bottom in a row with their
center axes extending parallel to one another and joining their adjacent
walls. Thus, the hollow housing 28 will include three housing spaces 26
that are each extending linearly in the vertical direction with
unchanging circular cross section and open at the bottom face, and that
are arrayed at prescribed intervals on a straight line.

[0041]A support projection 32 for linking and support purposes is formed
projecting upward from the center of the upper face of the hollow housing
28; a screw hole 34 for mounting purposes is provided in this support
projection 32. Furthermore, the lower end section of the hollow housing
28 projects slightly towards the outside peripheral direction at either
end in the lengthwise direction (sideways in FIG. 1), which represents
the direction of array of the three housing spaces 26.

[0042]The hollow housing 28 is formed of metal or similar material having
rigidity and strength sufficient to not experience deformation etc. due
to contact of a mass member 30, which will be described later. In
consideration of the ease of the forming operation, production cost, and
so on, it may be formed of cast iron, for example. In order to ensure a
high degree of dimensional accuracy for each of the housing spaces 26, it
will be preferable to finish the peripheral walls and upper walls by a
cutting process subsequent to casting.

[0043]Meanwhile, the fastener plate 24 is affixed to the lower side of the
hollow housing 28. The fastener plate 24 is formed of metal or similar
material having rigidity and strength sufficient to not experience
deformation etc. due to contact against a fastener wall portion 116,
discussed later; in consideration of the ease of the forming operation,
production cost, and so on, it may be formed of cast iron, for example.
The fastener plate 24 is generally rectangular in shape and has
prescribed thickness dimension; its shape is such that it can
continuously cover the openings of the three housing spaces 26 formed in
the hollow housing 28, while in the lengthwise direction which represents
the direction of array of the housing spaces 26 (the sideways direction
in FIG. 1), it has length dimension so as to project out beyond the
hollow housing 28. Cushion covers 36 formed of a rubber elastic body are
attached to the two lengthwise ends of the fastener plate 24 projecting
out from the hollow housing 28, with the upper and lower faces and the
side faces at the two lengthwise ends being covered by the cushion covers
36.

[0044]The fastener plate 24 is mounted by welding, bolts, etc. onto the
lower face of the hollow housing 28. The openings of the three housing
spaces 26 in the hollow housing 28 are thereby covered in their entirety
by the upper face of the fastener plate 24. The upper face of the
fastener plate 24 at locations thereof situated facing the openings of
the three housing spaces 26 is a flat surface extending in the horizontal
direction over the entire face. The lower outside peripheral edge of the
hollow housing 28 and the upper face of the fastener plate 24 juxtaposed
thereagainst are in generally intimate contact, isolating the three
housing spaces 26 from the space outside.

[0045]The mass member 30 is housed within each of the housing spaces 26.
FIG. 2 depicts the mass member 30. The mass member 30 is constructed with
an upper cushion cover 40 attached to the axial upper end of a mass
fitting 38 having solid cylindrical block shape, and with a lower cushion
cover 42 attached to the axial lower end of the mass fitting 38.

[0046]The mass fitting 38 has a solid cylindrical block shape of circular
cross section endowed with slightly smaller outside dimension than the
inside diameter dimension of the housing space 26 and formed with an
axial dimension smaller than the depth dimension of the housing space 26.
It is formed of iron or other metal material of high specific gravity.

[0047]The upper cushion cover 40 has a tubular portion 46 of round tubular
shape integrally formed so as to extend downward from the outside
peripheral edge of an upper base portion 44 of annular disk shape,
producing a rotating body contour that extends in the circumferential
direction with a thin cross section of inverted "L" shape. On the upper
face of the upper base portion 44 is integrally formed an annular rib
projection 48 extending in the circumferential direction through the
diametrically medial section and projecting axially upward; and on the
outside peripheral face of the tubular portion 46 are integrally formed
annular rib projections 50, 50 extending in the circumferential direction
through the axially medial section and projecting diametrically outward.

[0048]The upper cushion cover 40 is integrally formed by a rubber elastic
body which is a separate element from the mass fitting 38; the inside
diameter dimension of the tubular portion 46 is slightly small than the
outer dimension of the mass fitting 38. This separate upper cushion cover
40 is secured fitting externally onto the upper end of the mass fitting
38, performing an adhesive treatment if needed. Then, with the upper base
portion 44 juxtaposed in intimate contact with the outside peripheral
edge of the upper end face of the mass fitting 38, and the tubular
portion 46 juxtaposed in intimate contact with the outside peripheral
face of the upper end of the mass fitting 38, the corners of the upper
end of the mass fitting 38 are covered in their entirety by the upper
cushion cover 40.

[0049]A lower cushion cover 42 has a base wall portion 54 integrally
formed in the axial lower section of a tubular portion 52 of round
tubular shape; and is integrally formed by a rubber elastic body of
generally bottomed round cylindrical shape overall which constitutes a
separate element from the mass fitting 38. On the outside peripheral face
of the tubular portion 52 are integrally formed annular ribs 56, 56
extending in the circumferential direction through the axially medial
section and projecting diametrically outward.

[0050]In the center portion of the base wall portion 54 of the lower
cushion cover 42 is integrally formed a strike portion 58 of block shape
which projects axially downward with circular cross section; and a
support leg portion 60 of tapered shape or funnel shape sloping towards
the outside peripheral side at a prescribed angle axially upward from the
outside peripheral face of the basal end (upper end) of the strike
portion 58 is formed such that the outside peripheral edge of this
support leg portion 60 is integrally linked with the lower peripheral
edge of the tubular portion 52.

[0051]The inside diameter dimension of the tubular portion 52 is slightly
smaller than the outside diameter dimension of the mass fitting 38, and
the lower cushion cover 42 is secured fitting externally onto the lower
end of the mass fitting 38, performing an adhesive treatment if needed.
Specifically, the tubular portion 52 is juxtaposed in intimate contact
against the outside peripheral face of the lower end of the mass fitting
38, and the support leg portion 60 of the base wall portion 54 is
positioned extending over the lower end face of the mass fitting 38,
whereby the lower end section, including the lower end face of the mass
fitting 38, is covered in its entirety by the lower cushion cover 42.

[0052]At the outside peripheral edge of the upper end face of the support
leg portion 60 is integrally formed a support projection 62 which
projects upward in the connecting corner portion with the tubular portion
52 and which extends around the entire circumference in the
circumferential direction; the outside peripheral edge of the support leg
portion 60 is supported in contact against the outside peripheral edge of
the lower end face of the mass fitting 38 by this support projection 62.
Thus, with the lower cushion cover 42 installed on the mass fitting 38,
the support leg portion 60 and the strike portion 58 are positioned
substantially entirely below and spaced apart from the lower end face of
the mass fitting 38, thus creating between the axially opposing faces of
the support leg portion 60 and the strike portion 58 and the lower end
face of the mass fitting 38 a hollowed space 64 that permits axial
displacement of strike portion 58 on the basis of elastic deformation of
the support leg portion 60.

[0053]Furthermore, the projecting distal end face (axial lower end face)
of the strike portion 58 constitutes a strike face 66 of circular shape
positioned on the center axis of the mass fitting 38 and extending
perpendicular to this center axis. On the strike face 66 is integrally
formed an annular rib projection 68 that extends in the circumferential
direction through the diametrically medial section about the center axis
and projects axially downward; this element is adapted to adjust initial
spring characteristics when the strike face strikes 66 against the
fastener plate 24, and to reduce noise etc.

[0054]In preferred practice, the strike portion 58 with the rib projection
68 will have at its strike face 66 Shore D hardness (per ASTM standard
D2240) of 80 or lower and modulus of compression in the axial direction
of between 1 and 104 MPa, as well as loss tangent of 10-3 or
above. On the axial upper end face of the strike portion 58 is integrally
formed an annular rib projection 70 that extends in the circumferential
direction about the center axis and projects axially upward. The rib
projection 70, which projects towards the axial lower end face of the
mass fitting 38 within the hollowed space 64 is designed to ameliorate
shock and noise when the strike portion 58 strikes the mass fitting 38
during excessive deformation of the support leg portion 60.

[0055]While not illustrated in detail, in the present embodiment, in order
to adjust the spring characteristics of the support leg portion 60, thin
portions of arcuate shape each of prescribed width and having length
approximately equal to one-fourth of the circumference in the
circumferential direction are formed in the inside peripheral edge
section of the lower end face of the support leg portion 60, to either
side of the strike portion 58. A through-hole perforates the center
section of each thin portion; the hollowed space 64 communicates with the
outside (i.e. with the housing space 26) through these through-holes,
whereby the hollowed space 64 acts as an air spring, while not hampering
displacement of the mass fitting 38, discussed later.

[0056]The mass members 30 described above are installed housed within the
three housing spaces 26 of the hollow housing 28. When installed in this
way, the mass members 30 are able to ricochet in the axial direction
within the housing spaces 26 and undergo reciprocating displacement
independent of the hollow housing 28.

[0057]In the present embodiment, the mass members 30 are designed so that
the rib projections 50, 56 in the tubular portions 46, 52 of the upper
and lower cushion covers 40, 42 of maximum outside diameter dimension
each have outside diameter dimension smaller by between 0.1 and 1.6 mm
than the inside diameter dimension of the housing spaces 26 of the hollow
housing 28. Thus, the axial dimension from the projecting distal end of
the rib projection 48 on the upper base portion 44 of the upper cushion
cover 40 to the projecting distal end of the rib projection 68 on the
strike face 66 of the strike portion 58 of the lower cushion cover 42,
which represents the maximum axial length dimension, is at least 1.0 mm
smaller, and preferably between 1.0 and 3.0 mm smaller, than the distance
between the opposing faces of the upper base face of the housing space 26
and the upper face of the fastener plate 24. The maximum axial length
dimension of the mass member 30 is based on that with the mass member 30
stationary, and the lower cushion cover 42 elastically deformed by a
prescribed amount under the weight of the mass fitting 38.

[0058]In all likelihood, if the diametrical gap between the mass member 30
and the housing space 26 is too small, during vibration input the mass
member 30 will tend to slide easily along the inside wall of the housing
space, making it difficult to effectively achieve relative axial
displacement of the mass member 30 with respect to the hollow housing 28
and vibration damping action on the basis thereof. On the other hand if
the diametrical gap between the mass member 30 and the housing space 26
is too large, during vibration input the mass member 30 will tend to
experience tilting or other irregular displacement, making it difficult
to achieve consistent vibration damping action. In the axial direction of
the mass member 30, meanwhile, there will be no problems as long as the
size of the housing space 26 is such that the mass member 30 is
substantially independently displaceable with the respect to the hollow
housing 28, but if this is too large it will constitute a waste of space.

[0059]In order for the strike face 66 of the lower cushion cover 42 to
separate completely from the upper face of the fastener plate 24 during
ricochet displacement of the mass member 30 it will be necessary to
ensure in the axial dimension of the housing space 26 the equivalent of
the axial length of the mass member 30 in the absence of the influence of
the weight of the mass fitting 38 and of deformation of the lower cushion
cover 42. Otherwise, it is sufficient for the mass member 30 to exert
effective repeated load (dynamic load) on the hollow housing 28 through
relative displacement with respect to the hollow housing 28, and it will
not be necessary for the strike face 66 of the lower cushion cover 42 to
physically separate from the upper face of the fastener plate 24 during
ricochet displacement of the mass member 30. In the present embodiment in
particular, the direction of displacement of the mass member 30 is
approximately coincident with the direction of gravity and the mass
member will be returned to the home position under the effect of gravity.
Thus it will not be necessary for the upper cushion cover 40 to strike
the upper base face of the housing space 26 during input of vibration to
be damped, making it possible to achieve the desired vibration damping
action simply through striking of the lower cushion cover 42 against the
fastener plate 24 and exerting effective repeated load thereby.

[0060]Meanwhile, in the present embodiment in particular, a lower damper
mass 22b is installed on the opposite side of the fastener plate 24 from
the upper damper mass 22a, i.e., on the lower face of the fastener plate
24. The lower damper mass 22b is generally similar in structure to the
upper damper mass 22a and will not be described in detail except to note
that the hollow housing 28 constituting the lower damper mass 22b is
attached to the fastener plate 24 in a condition equivalent to flipping
the hollow housing 28 in the upper damper mass 22a top to bottom, i.e.
with the openings of the three housing spaces 26 covered in their
entirety by the lower face of the fastener plate 24. The upper outside
peripheral edge of the hollow housing 28 and the lower face of the
fastener plate 24 juxtaposed thereagainst are in generally intimate
contact, isolating the three housing spaces 26 from the space outside.

[0061]Mass members 30 of similar structure to those in the upper damper
mass 22a described earlier are housed within these three housing spaces
26. While the mass members 30 housed in the lower damper mass 22b have
similar structure to the mass members 30 housed in the upper damper mass
22a, the mass members 30 housed in the lower damper mass 22b are housed
with their vertical direction oriented identically to the mass members 30
housed in the upper damper mass 22a. Specifically, the three mass members
30 housed in the hollow housing 28 of the lower damper mass 22b are
arranged housed therein with the upper cushion cover 40 positioned
plumb-vertically above and the lower cushion cover 42 positioned
plumb-vertically below, and with the rib projection 68 and the strike
face 66 of the strike portion 58 of the lower cushion cover 42 contacting
the lower base face of the housing space 26 formed in the hollow housing
28.

[0062]In the present embodiment, the damper mass 14 is thereby constituted
by mounting the upper damper mass 22a on the upper side of the fastener
plate 24 and the lower damper mass 22b on the lower side. The total mass
of the damper mass 14 will preferably equal between 5 and 15% of the mass
of the vibrating member 20. The reason is that if the mass of the damper
mass 14 is less than 5% of the mass of the vibrating member 20, it may be
difficult to achieve effective vibration damping action in some
instances, whereas in excess of 15% the increased weight of the apparatus
as a whole tends to be problem. Furthermore, in order to achieve
effective vibration damping action based on striking against the hollow
housing 28, it is preferable for the mass of the independent mass members
30 to be such that total mass of the several mass members 30 is equal to
between 5 and 10% of the mass of the vibrating member 20. Where multiple
such vibration damping apparatus 10 are furnished to a vibrating member
20, the total mass of all of the damper masses 14 provided to the
multiple vibration damping apparatus 10 will preferably be equal to
between 5 and 15% of the mass of the vibrating member 20; and the total
mass of all of the independent mass members 30 will preferably be equal
to between 5 and 10% of the mass of the vibrating member 20.

[0063]The damper mass 14 having the structure described above is attached
to the two brackets 12a, 12b via the plate spring stuffs 16 and the
rubber bushings 18 disposed at top and bottom. FIG. 3 depicts the upper
face of one of the plate spring stuffs 16. The plate spring stuff 16 is
fabricated of sheet steel or other metal and has a thin contour extending
with generally unchanging thickness dimension. The plate spring stuff 16
is also left-right symmetrical in shape, with its width dimension in top
view varying along the lengthwise direction, becoming widest in its
center portion 72, and with its medial portions extending towards end
portions 74 situated at both ends constituting necked portions 76 that
are bowed at the edges on either side so as to create the smallest width
dimension. In top view the two end portions 74 have equal width
dimension, with the width dimension of the two end portions 74 being
somewhat smaller than the width dimension of the center portion 72.

[0064]A center attachment plate 78 of strip shape is welded to the upper
face of the center portion 72 of the plate spring stuff 16, and an end
attachment plate 80 of strip shape is welded to the upper face at each of
the two end portions 74. The center attachment plate 78 and the end
attachment plates 80, like the plate spring stuff 16, are fabricated of
steel sheet etc.; the lengthwise dimension of the center attachment plate
78 is equal to the lengthwise dimension of the center portion 72, while
the lengthwise dimension of the end attachment plates 80 is slightly
smaller than the lengthwise dimension of the end portions 74. These are
each welded to the plate spring stuff 16 so as to extend across its
width. Pairs of through-holes 82 perforating through the thickness of the
center attachment plate 78 or end attachment plate 80 and the plate
spring stuff 16 therebelow are formed in a row in the lengthwise
direction of the attachment plates 78, 80, in other words, along the
width of the plate spring stuff 16.

[0065]Meanwhile, the rubber bushings 18 which support the two ends
portions 74 of the plate spring stuff 16 have a structure in which an
inner tubular fitting 86 constituting an inner shaft member of round
tubular shape having outside diameter dimension smaller than the inside
diameter dimension of an outer tubular fitting 84 constituting an outer
tubular member of round tubular shape is positioned inserted through the
outer tubular fitting 84 so as to be coaxial therewith and spaced apart
diametrically therefrom, with the two fittings linked in the diametrical
direction by a main rubber elastic body 88 as the rubber elastic body.
More specifically, a bushing internal member 89 constituted to include
the inner tubular fitting 86 and the main rubber elastic body 88 is
secured press-fit into the outer tubular fitting 84. The bushing internal
member 89 is a vulcanization-molded component produced by inserting the
inner tubular fitting 86 into a press-fit tubular fitting 91 of
thin-walled round tubular shape having outside diameter dimension
slightly smaller than the inside diameter dimension of the outer tubular
fitting 84 and axial dimension approximately equal to the axial dimension
of the outer tubular fitting 84, and positioning the inner tubular
fitting 86 therein so as to be coaxial therewith and spaced apart
diametrically therefrom; filling the space between the press-fit tubular
fitting 91 and the inner tubular fitting 86 with the main rubber elastic
body 88; and subjecting these to integral vulcanization molding. The
press-fit tubular fitting 91 of the bushing internal member 89 is then
subjected to a constriction process to pre-compress the main rubber
elastic body 88, and the bushing internal member 89 is then press-fit
into the outer tubular fitting 84. A rubber bushing 18 in which the inner
tubular fitting 86 is positioned passing coaxially through the outer
tubular fitting 84, and in which the outer tubular fitting 84 and the
inner tubular fitting 86 are linked in the diametrical direction by the
main rubber elastic body 88, is formed thereby.

[0066]As shown in FIG. 4, the axial dimension of the inner tubular fitting
86 is such that it spans the distance between the front wall portion 90
and the rear wall portion 92 of the bracket 12a which has a generally
three-sided square contour in top view, and is somewhat larger than the
axial dimension of the outer tubular fitting 84. The main rubber elastic
body 88 disposed between the outer tubular fitting 84 and the inner
tubular fitting 86 has a round tubular contour extending straight with an
unchanging annular cross section.

[0067]A linking member 94 is welded to the outside peripheral face of the
outer tubular fitting 84. The linking member 94 is formed of metal etc.
similar to the outer tubular fitting 84 and the inner tubular fitting 86;
and has a generally "<" shaped cross section contour with a flat
tabular portion 96 as well as a curving portion 98 that extends from one
edge of the tabular portion 96 and curves at curvature ratio
approximately the same as the curvature ratio of the outside peripheral
face of the outer tubular fitting 84. An upright wall 100 is integrally
formed with the two edges of the linking member 94 in the width direction
(the vertical direction in FIG. 4). Here, the width dimension of the
linking member 94 is slightly larger than the axial dimension of the
outer tubular fitting 84, and slightly smaller than the axial dimension
of the inner tubular fitting 86 as well. The linking member 94 is then
secured by welding to the outer tubular fitting 84, with the curving
portion 98 juxtaposed against the outside peripheral wall of the outer
tubular fitting 84. The linking member 94 is attached to the outer
tubular fitting 84 such that, in the mounted state, an extended line in
the direction of extension of the tabular portion 96 will pass through
approximately the same center axis as the outer tubular fitting 84 and
the inner tubular fitting 86.

[0068]Rubber bushings 18 constructed in this way are attached respectively
to the upper and lower ends of the two brackets 12a, 12b. Since the
method of attaching these four rubber bushings 18 to the brackets 12a,
12b is the same for each, the example of the rubber bushing 18 attached
to the upper end of the bracket 12a as shown in FIG. 4 will be described
here. First, with the linking member 94 facing the open side of the
bracket 12a (the left side in FIG. 4), the rubber bushing 18 is inserted
between the front wall portion 90 and the rear wall portion 92 of the
bracket 12a. Here, the upper ends of the front and rear wall portions 90,
92 of the bracket 12a are perforated by bolt holes (not shown) having
outside diameter dimension approximately equal to the inside diameter
dimension of the inner tubular fitting 86. The rubber bushing 18 is
positioned so that the center axis of the inner tubular fitting 86 is
aligned with the center axes of the bolt holes made in the bracket 12a.
Then, in the positioned state, a bolt 102 is passed through the bolt
holes and the inner tubular fitting 86, from the outside of either the
front or rear wall portion 90, 92 of the bracket 12a (in FIG. 4, from the
front wall portion 90).

[0069]The axial dimension of the bolt 102 is greater than the width
dimension of the bracket 12a in the front-back direction; the bolt 102 is
passed through the bracket 12a in the front-back direction with its head
104 detained by the outside face of either the front or rear wall portion
90, 92 (in FIG. 4, from the front wall portion 90), and with its distal
end 106 projecting to the outside of either the front or rear wall
portion 90, 92 (in FIG. 4, the rear wall portion 92). A nut 108 is then
tightened onto the distal end 106 projected to the outside of the bracket
12a, and the nut 108 is secured by welding to the outside face of either
the front or rear wall portion 90, 92 (in FIG. 4, the rear wall portion
92), thereby attaching the bolt 102 so as to span the bracket 12a front
to back. The rubber bushing 18 attached to the bracket 12a through the
inner tubular fitting 86 of the rubber bushing 18 fitting on the outside
of the bolt 102.

[0070]The nut 108 is tightened to an extent such that the front and rear
wall portions 90, 92 of the bracket 12a clamp and compress the two axial
end faces of the inner tubular fitting 86 of the rubber bushing 18,
rendering the rubber bushing 18 unable to turn with respect to the
bracket 12a. In this attached state, slight gaps form between the two
side edges of the linking member 94 and the front and rear wall portions
90, 92. Each rubber bushing 18 is attached in such a way that the curving
portion 98 its respective linking member 94 is positioned to the inside
of the brackets 12a, 12b. Thus, as will be apparent from FIG. 1, the
rubber bushings 18 installed at the upper ends and lower ends of the
brackets 12a, 12b are attached facing in mutually opposite directions top
and bottom.

[0071]Optionally, a locking mechanism or the like could be employed to
prevent the rubber bushing 18 from turning. In the present embodiment,
the inner tubular fitting 86 having a tubular contour is used as the
inner shaft member. However, it would be acceptable for example to
instead use a solid shaft member as the inner shaft member, and to
arrange this shaft member so as to pass through through-holes perforating
the front and rear wall portions 90, 92 to attach the rubber bushing 18
to the bracket 12a; and to employ a locking mechanism etc. to prevent the
rubber bushing 18 from turning. Furthermore, whereas in the present
embodiment the main rubber elastic body 88 is linked to the outer tubular
fitting 84 via the press-fit tubular fitting 91, the main rubber elastic
body 88 could instead be linked directly to the outer tubular fitting 84
and the inner tubular fitting 86, without the intervening press-fit
tubular fitting 91.

[0072]The plate spring stuffs 16 are attached to the rubber bushings 18
installed at both the upper and lower end of each bracket 12a, 12b. Each
of the plate spring stuffs 16 is positioned with the face thereof
situated opposite that to which the end attachment plates 80 are attached
to the end portions 74 juxtaposed against the tabular portion 96 of the
linking member 94 of the rubber bushings 18, and are affixed to the
tabular portion 96 by rivet welds, bolts, etc. Here, an end attachment
plate 80 edge lying towards the center portion 72 and the distal edge of
the tabular portion 96 projecting towards the center portion 72 are
aligned in approximately the same position in top view, thereby securely
holding the end portion 74 of the plate spring stuffs 16 clamped from
above and below, while not constraining deformation in areas other than
those juxtaposed against the tabular portions 96.

[0073]With this arrangement, the two end portions 74 of the pair of plate
spring stuffs 16 are affixed to the rubber bushings 18 provided at the
upper and lower ends of the brackets 12a, 12b; and the two brackets 12a,
12b are linked by the rubber bushings 18 disposed at top and bottom, and
by the pair of plate spring stuffs 16 spanning therebetween. The plate
spring stuffs 16 are positioned spaced apart in the direction of input of
vibration to be damped (the vertical direction in FIG. 1) as well.

[0074]The damper mass 14 having the structure discussed earlier is then
positioned between the plate spring stuffs 16, 16 which respectively span
the top and bottom of the brackets 12a, 12b. The damper mass 14 is
attached with the support projection 32 projected from the hollow housing
28 of the upper damper mass 22a juxtaposed against the center portion 72
of the plate spring stuff 16 situated on the top side, by passing the
mounting bolt 110 through the through-hole 82 perforating the center
portion 72 of the plate spring stuff 16 and inserting it into the screw
hole 34 of the support projection 32 thereby attaching it to the plate
spring stuff 16 situated on the top side; and with the support projection
32 of the hollow housing 28 of the lower damper mass 22b similarly
juxtaposed against the center portion 72 of the plate spring stuff 16
situated on the bottom side and attached thereto by the mounting bolt
110. While not necessarily clear from the drawings, in the present
embodiment, the screw holes 34, 34 corresponding in location to the
through-holes 82, 82 of the plate spring stuffs 16 are formed in the
support projections 32, 32; and the mounting bolts 110, 110 are inserted
into the pair of screw holes 34, 34. That is, the damper mass 14 of the
present embodiment is fastened to each of the plate spring stuffs 16 by
there two mounting bolts 110, 110. The respective plate spring stuffs 16
are each attached to the damper mass 14 so as to be clamped between the
upper end face of the hollow housing 28 support projection 32 and the
center attachment plate 78 which is affixed to the center portion 72 of
the plate spring stuff 16, and securely attached thereto under the
clamping force of the mounting bolt 110 which is effectively exerted
across the entire width of the center portion 72 of the plate spring
stuff 16 through the agency of the center attachment plate 78. The
dimension of the support projection 32 and the dimension of the center
attachment plate 78 are approximately equal in plan view, and deformation
is not constrained in areas of the plate spring stuffs 16 other than
those pushed against by the center attachment plate 78.

[0075]In the present embodiment, the damper mass 14 is attached to the
center portion 72 of the plate spring stuffs 16 in this way, with the two
end portions 74 of the plate spring stuffs 16 extending out to either
side of the damper mass 14 in the horizontal direction. Plate springs 111
serving as a pair of plate spring that span the damper mass 14 and the
vibrating member 20 are constituted by sections of the plate spring stuff
16 situated to either horizontal side of the damper mass 14, i.e. between
the center portion 72 and the end portions 74, with the plate spring
stuff 16 center portion 72 which constitutes a first end portion of each
plate spring 111 being attached to the damper mass 14, and the plate
spring stuff 16 end portions 74 which constitute the other end portions
of the plate springs 111 attached to the rubber bushings 18; and are
mounted thereby on the vibrating member 20 via the rubber bushings 18 and
the brackets 12a, 12b.

[0076]Furthermore, the plate spring stuffs 16 are left-right symmetrical,
whereby an elastic support center axis 112 composed of multiple (in the
present embodiment, four) plate springs 111 is established so as to pass
in the plumb-vertical direction through the center of the plate spring
stuffs 16. A vertical line passing through the center of gravity of the
damper mass 14 is approximately aligned with the elastic support center
axis 112 composed of the plate springs 111. With this arrangement,
excitation force produced on the basis of displacement of the damper mass
14 and exerted on the plate spring stuffs 16 will be exerted generally
along the elastic support center axis 112. Moreover, since the center of
gravity of the damper mass 14 is situated approximately on the elastic
support center axis 112 of the plate spring stuffs 16, irregular
displacement of the damper mass 14 in the twisting direction etc. will be
reduced, and displacement in the plumb-vertical direction will be
produced consistently, during displacement excitation of the damper mass
14. Furthermore, in the present embodiment in particular, by positioning
the plate spring stuffs 16 above and below the damper mass 14 and
supporting the top and bottom of the damper mass 14 by the plate spring
stuffs 16, irregular displacement of the damper mass 14 in the twisting
direction etc. will be effectively reduced.

[0077]As mentioned earlier, the brackets 12a, 12b have a generally
three-sided square contour in top view, with the front wall portion 90
and the rear wall portion 92 positioned in opposition. Slots 114 are
formed in the vertical center section of the front and rear wall portions
92, and fastener wall portions 116 that extend upright towards the
bracket 12 interior are formed on the upper and lower sides of the slots
114 and on the peripheral edges therebetween. The edges of the fastener
plate 24 of the damper mass 14 are positioned within these slots 114. The
height dimension of the slots 114 is such that displacement of the damper
mass 14 is permitted during ordinary vibration input, within a range such
that the cushion covers 36 provided at the two ends of the fastener plate
24 do not strike against the fastener wall portions 116. In the event
that input of an impact load etc. gives rise to an excessive level of
displacement, the fastener plate 24 will strike against the fastener wall
portions 116 via the intervening cushion covers 36, thereby providing
cushioned restriction of the amount of displacement by the damper mass 14
and the amount of elastic deformation of the plate spring stuffs 16 and
the rubber bushings 18.

[0078]The vibration damping apparatus 10 having the structure described
above is secured to the vibrating member 20 by attaching the rear wall
portion 92 of the brackets 12a, 12b thereto with mounting bolts 118 etc.
The damper mass 14 is thereby elastically mounted on the vibrating member
20 of the primary vibrating system, via the plate spring stuffs 16 and
the rubber bushings 18, thereby constituting a secondary vibrating system
in which the damper mass 14 serves as the mass, and the plate spring
stuffs 16 and the rubber bushings 18 serve as springs, so as to afford
overall dynamic damper functionality. Thus, through proper adjustment of
the mass of the damper mass 14 and of the dynamic spring constant of the
plate spring stuffs 16 and the rubber bushings 18, the characteristic
frequency of the secondary vibrating system can be tuned to the frequency
of the vibration to be damped in the vibrating member 20, so that the
vibration damping action of the vibration damping apparatus is exerted on
the vibrating member 20.

[0079]Moreover, since the vibration damping apparatus 10 has mass members
30 positioned housed within the interior of the damper mass 14
constituting the mass of the secondary vibrating system in such a way
that they are independently displaceable in the vertical direction, which
is also the direction of vibration input, through relative displacement
of the mass members 30 with respect to the hollow housing 28 and their
action of striking against the hollow housing 28 when vibration is input,
the vibration damping action of the vibration damping apparatus 10 will
be further improved and better vibration damping action with respect to
the vibrating member 20 will be achieved.

[0080]Furthermore, in the present embodiment in particular, the two end
portions 74 of the plate spring stuffs 16 are attached to the brackets
12a, 12b via main rubber elastic body 88 of the rubber bushings 18, and
attached such that the direction of input of load exerted on the plate
spring stuffs 16 by the damper mass 14 during vibration input will exert
moment in approximately the circumferential direction of the main rubber
elastic body 88 which has round tubular shape, in other words, in the
torsional direction of the main rubber elastic body 88. Thus, the load
bearing on the plate spring stuffs 16 during vibration input will act in
the torsional direction of the main rubber elastic body 88 via the
linking member 94 and the outer tubular fitting 84 of the rubber bushings
18, and low dynamic spring constant will be observed on the part of the
main rubber elastic body 88. Consequently, in the event that the damper
mass 14 has been induced to undergo displacement during vibration input,
due to the ease of deformation by the main rubber elastic body 88 the two
end portions 74 of the plate spring stuffs 16 will be able to deform in
response to displacement of the damper mass 14, thereby reducing the
tensile stress to which the plate spring stuffs 16 are subjected, and
suppressing a sharp rise in the dynamic spring constant of the plate
spring stuffs 16 in the form of tensile rigidity. As a result,
satisfactory bending elasticity of the plate spring stuffs 16 can be
advantageously assured, and a wider region affording linear
characteristics of the plate spring stuffs 16 can be assured without
having to increase the length dimension of the plate spring stuffs 16, so
that better vibration damping action may be achieved. Additionally, since
the length dimension of the plate spring stuffs 16 can be kept small, the
vibration damping apparatus can be compact, and durability of the plate
spring stuffs 16 can be advantageously assured as well.

[0081]In the present embodiment in particular, utilizing the length
dimension from the center portion 72 to the end portions 74 of the plate
spring stuff 16, there is constituted a lever having the center portion
72 where the damper mass 14 is attached as its working point and exerting
load on the main rubber elastic body 88, whereby moment in the torsional
direction may be effectively exerted on the main rubber elastic body 88,
and torsional deformation of the main rubber elastic body 88 may be
readily brought about.

[0082]FIG. 5 depicts by way of an example the results of measuring change
in applied load when the plate spring stuffs 16 are induced to undergo
displacement by a prescribed amount in the vibration damping apparatus 10
having the structure described above. The horizontal axis in FIG. 5 shows
displacement of the plate spring stuffs 16 (unit: mm), and the vertical
axis shows the load bearing on the plate spring stuffs 16 (unit: N). By
way of a comparative example, FIG. 5 also shown as a comparative example
the results of measurements made in the same way, but with the plate
spring stuffs 16 attached directly to the brackets 12a, 12b without the
rubber bushings 18 interposed.

[0083]As shown in FIG. 5, with the comparative example a sharp nonlinear
change in characteristics of the plate spring stuffs 16 was observed in
association with increasing deformation of the plate spring stuffs 16;
whereas with the example of the vibration damping apparatus 10 having the
aforementioned structure, linear characteristics of the plate spring
stuffs 16 were assured over a wide range through deformation of the main
rubber elastic body 88 provided to the rubber bushings 18.

[0084]Next, FIG. 6 depicts a vibration damping apparatus 130 pertaining to
a second embodiment of the present invention. This embodiment shows a
specific example of plate spring stuffs that differ in shape from those
of the vibration damping apparatus 10 in the first embodiment; components
and areas that are similar in structure to those of the vibration damping
apparatus 10 pertaining to the first embodiment are identified in the
drawings using the same symbols as in the first embodiment, and will not
be discussed in any detail.

[0085]In the vibration damping apparatus 130 of the present embodiment,
plate spring stuffs 132 which are bent in side view extend between rubber
bushings 18 which are attached at the upper and lower ends of brackets
12a, 12b. The plate spring stuffs 132 have upper face contours similar to
the plate spring stuffs 16 in the preceding first embodiment (see FIG.
2). The plate spring stuffs 132 in the present embodiment have bending
portions 134 situated between the center portion 72 and the end portions
74 and bent in a corrugated pattern in side view. The number of
corrugations formed in the bending portions 134 is not limited to any
particular number. It would be acceptable, for example, to formed a
multitude of corrugations having short length, or a single arcuate shape
extending from the end portion 74 to the center portion 72. The bending
portions 134 is formed in zones situated between the end portions 74 and
the center portion 72 but excluding the areas where the end attachment
plates 80 and the center attachment plate 78 are affixed; as with the
plate spring stuffs 16 in the first embodiment, the areas where the end
attachment plates 80 and the center attachment plate 78 are flat.

[0086]Like the plate spring stuffs 16 in the first embodiment, the pair of
plate spring stuffs 132 having the above structure are respectively
fastened with rivets or bolts to tabular portion 96 of the linking member
94 of the rubber bushings 18 attached to the upper ends of the brackets
12a, 12b and of the rubber bushings 18 attached to the lower ends of the
brackets 12a, 12b, so as to span the distance between the two rubber
bushings 18. The center portion 72 of the plate spring stuff 132 situated
at top is then juxtaposed against the support projection 32 projecting
from the hollow housing 28 which constitutes the upper damper mass 22a,
and is secured in place by a mounting bolt 110; while the center portion
72 of the plate spring stuff 132 situated at bottom is juxtaposed against
the support projection 32 projecting from the hollow housing 28 which
constitutes the lower damper mass 22b, and is secured in place by a
mounting bolt 110, thereby positioning the damper mass 14 between these
two plate spring stuffs 132. As in the first embodiment discussed
previously, by attaching the damper mass 14 to the plate spring stuffs
132 at their center portion 72, a pair of plate springs 136 situated to
either side of the damper mass 14 are formed by sections of the plate
spring stuffs 132 lying between their center portion 72 and their end
portions 74; and the bending portions 134 are formed in these plate
springs 136.

[0087]In the vibration damping apparatus 130 having the above structure,
when the damper mass 14 is displaced, the bending portions 134 of the
plate springs 136 will expand. It is possible thereby to ensure
substantially large length dimension of the plate springs 136, and to
suppress the occurrence of reaction force to extension of the plate
springs 136. As a result, linear characteristics of the plate springs 136
can be assured over a wider range, and better vibration damping action
will be possible.

[0088]While the present invention has been described hereinabove through
certain preferred embodiments, these are merely exemplary and should not
be construed as limiting the invention to the specific disclosure herein.

[0089]For example, the specific structure of the mass members used in the
present invention is not limited to that in the preceding embodiments; it
would of course be possible to provide independent mass members 30 in a
number greater than or less than that taught in the embodiments above, by
way of the number of mass members 30 housed within the damper mass 14.
Moreover, the multiple mass members 30 housed in the damper mass 14 need
not necessarily have identical shape and size, and may differ in size,
for example. Furthermore, as the mass members it would be possible to
employ mass members of block form, rather than independent mass members.

[0090]In the preceding embodiments, the plate springs are disposed at
either side, i.e. both top and bottom, in the direction of vibration
input to the mass members; however, it would be possible to provide a
plate spring only at the top or bottom of the mass members.

[0091]Furthermore, whereas in the preceding embodiments the mass member is
attached to the plate spring at the center portion so that the plate
spring extends out to the left and right sides of the mass member
allowing the mass member to be supported at the left and right sides, it
would be acceptable to instead extend the plate spring to either the left
or right side only, so that the mass member is supported in cantilever
fashion at either the right or left side, for example.

[0092]Furthermore, the rubber bushings may be disposed on the mass member
side, or disposed on both the mass member side and the vibrating
component side. Consequently, in the damper mass 14 of the first
embodiment for example, either the outer tubular fitting 84 or the inner
tubular fitting 86 of the rubber bushings 18 could be attached to the
damper mass 14, and the other attached to the plate spring stuffs 16.

[0093]The present invention is not limited to vibration damping of
vibration in the plumb-vertical direction, and through proper alignment
of the elastic support center axis of the spring members with the
direction of input of vibration to be damped will afford effective
vibration damping action against vibration in either the horizontal
direction or on the diagonal.

[0094]Additionally, the vibration damping apparatus pertaining to the
present invention should be understood as being applicable to a wide
range of components whose vibration causes problems in an automotive
body, sub-frame, engine block, seats, steering components, instrument
panel, doors, mirrors etc., as well as various devices besides
automobiles.

[0095]It is also to be understood that the present invention may be
embodied with various other changes, modifications and improvements,
which may occur to those skilled in the art, without departing from the
spirit and scope of the invention defined in the following claims.